High levels of manganese oxides discovered by NASA’s Curiosity rover on Mars may indicate that oxygen was once abundant there. With last year’s discovery that the red planet may have been home to ancient lakes, it now seems more akin to our blue one.

“The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes,” said Nina Lanza, a planetary scientist at Los Alamos National Laboratory in New Mexico, while commenting on the potentially groundbreaking discovery.

The researchers point out that, judging by the geological setting in which the oxides were found, water and oxygen likely existed on Mars at the same time, particularly in the Gale Crater, where the Mars rover landed on August 6, 2012. The new discovery shows that, at some point in its development, Mars may have been rather similar to Earth.

“These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions. Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose,” added Lanza, discarding arguments that microbes may have played a role in producing the compounds.

Although the researchers don’t know exactly how oxygen ended up in the Martian atmosphere, Lanza suggests it was produced as water was split into hydrogen and oxygen when Mars’s protective magnetic field was disappearing. The light hydrogen atoms disappeared due to Mars’s low gravity, while oxygen was stored in the rocks, giving them the rusty red color that is Mars’ signature – and apparently forming manganese oxides. Interestingly, the amount of oxygen needed to make manganese oxides far exceeds the amount needed to turn the planet red. The new finding brings previous estimates of the quantities of oxygen that had been on Mars into question.

“It’s hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred. But it’s important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated,” Lanza stressed.

NASA’s Curiosity Mars rover embarked on an exploratory mission back in 2012. It has conducted geological and climate studies, among others, in an attempt to determine the role of water on Mars and find out whether the red planet might have ever supported life.

In October of 2015, the research team guiding the rover confirmed that, at some point between 3.8 and 3.3 billion years ago, the red planet may have stored large amounts of water.

“Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago,” the researcher said in a statement.